Are you a game designer with extensive experience in balancing competitive online games? If not, I hardly see how you're qualified to say that "pick rates and win rates" are the only way to balance a character.
The community's perception and feedback on a hero is also important. Any good game developer will listen to their community to identify heroes that need adjustment to keep the game fun and not extremely frustrating for their base. You should always give lots of weight to data to help inform decisions, but to say the ONLY data to look at is win/pick rate in a game where matches include 11 other heroes and a multitude of other variables is short-sighted at best.
I'm sure Blizzard collects extensive hero telemetry data that can be used to assess how the heroes are behaving during matches, whilst interacting with other heroes, etc. I'm also sure the game designers, developers, QA team, and Blizzard employees at large play the game daily and read community feedback daily. I doubt the decision to change him was made lightly, and you should trust Blizzard doesn't just change things because people are crying about it, but that community feedback IS a piece of the puzzle.